Field of the Disclosure
The present disclosure relates to a method and an apparatus for treating a raw-material powder in which the raw-material powder is treated with plasma.
Description of the Related Art
In recent years, fabrication devices that use the powder bed fusion technology (called 3D printers) have been under development. In powder bed fusion, a slice of a raw-material powder is formed, the region of each formed slice to be solidified (hereinafter referred to as the solidifying region) is irradiated with a laser beam or an electron beam (hereinafter referred to as an energy beam) to heat the solidifying region, and such slices are stacked to form a three-dimensional object (Japanese Patent Laid-Open Nos. 8-39275 and 10-88201).
It is generally believed that three-dimensional objects fabricated using powder bed fusion (hereinafter referred to as powder bed fusion products) can be strengthened by increasing the infill by reducing the void volume of the structure. Even in slices in which a spherical raw-material powder is the most closely packed, the interparticle void volume per unit volume exceeds 20%. This means that in the state that is called sintered, in which particles are fused only at the points of contact, there are countless voids between particles.
Japanese Patent Laid-Open No. 8-39275 proposes a powder bed fusion technique in which a three-dimensional object is fabricated through the formation of slices in an atmosphere supplied with an inert gas in an evacuated enclosure and heating of solidifying regions of the slices using a laser beam. Japanese Patent Laid-Open No. 10-88201 states that forming a shaped article from a raw-material powder without use of binder and compressing the raw-material powder before laser-beam powder bed fusion can increase the infill of the three-dimensional object.
The methods according to these publications for fabricating a three-dimensional object were found to fail to increase the infill of powder bed fusion products to sufficiently high levels because these methods leave very small voids in the structure of the finished three-dimensional object. The present disclosure aims to cure these shortcomings.